CareerCup

Time: O(n), Space: O(n)

public class DistinctPairs {
    public static void main(String[] args) {
        System.out.println(count(10, 1, 2, 3, 6, 7, 8, 9, 1) == 3);
        System.out.println(count(47, 6, 1, 3, 46, 1, 3, 9) == 1);
        System.out.println(count(9, 3, 2, 1, 45, 27, 6, 78, 9, 0) == 2);
        System.out.println(count(9, 3, 3, 2, 1, 45, 27, 6, 78, 9, 0) == 2);
        System.out.println(count(6, 1, 5, 7, -1) == 2);
        System.out.println(count(6, 1, 5, 7, -1, 5) == 2);
        System.out.println(count(2, 1, 1, 1, 1) == 1);
    }

    private static int count(int target, int... arr) {
        int count = 0;
        Set<String> seen = new HashSet<>();
        Set<Integer> set = new HashSet<>();
        for (int i = 0; i < arr.length; i++) {
            int k = target - arr[i];
            int[] pair = new int[]{k, arr[i]};
            Arrays.sort(pair);
            String s = Arrays.toString(pair);
            if (set.contains(k) && !seen.contains(s)) {
                count++;
                seen.add(s);
            } else {
                set.add(arr[i]);
            }
        }
        return count;
    }
}

private static void findCount(String[] strings) {
		
		Map<Set<Character>, Integer> patterns = new HashMap<>();
		for (String input : strings) {
			
			Set<Character> pattern = new TreeSet<>();
			for (char ch : input.toCharArray()) {
				pattern.add(ch);
			}
			if (patterns.containsKey(pattern)) {
				patterns.put(pattern, patterns.get(pattern)+1);
			} else {
				patterns.put(pattern, 1);
			}
		}
		for (Set<Character> exp : patterns.keySet()) {
			
			String s = exp.toString().replace("[", "").replace("]", "").replaceAll(", ", "");
			System.out.println(s + " " + patterns.get(exp));
		}
	}

public static String compress(String input) {

		if ((input == null) || input.isEmpty()) {
			return "";
		}

		int count = 1;
		String result = "";
		char prevChar = input.charAt(0);
		for (int i = 1; i < input.length(); i++) {

			char thisChar = input.charAt(i);
			if (thisChar == prevChar) {
				count++;
			} else {
				result += prevChar + "" + count;
				count = 1;
				prevChar = thisChar;
			}
		}
		result += prevChar + "" + count;
		return result;
	}

import java.util.ArrayList;
public class Alternate
{
 public static void main(String[] args)
{

int[] a = new int[] {-5, -2, 5, 2, 4, 7, 1, 0, 8, -8} ;			
ArrayList<Integer> negative = new ArrayList<Integer>() ;
ArrayList<Integer> positive = new ArrayList<Integer>() ;
				
for(int x : a)
{
  if(x < 0)
	negative.add(x) ;
  else
	positive.add(x) ;
}	

int nSize = negative.size() ;
int pSize = positive.size() ;
int[] b = new int[nSize+pSize] ;
int nCount = 0 , pCount = 0 ;

for(int i = 0 ; i < (nSize + pSize) || nCount < nSize || pCount < pSize ; i ++)
{
	if(i % 2 == 0 && nCount != nSize)
		b[i] = negative.get(nCount ++) ;
    else if(i % 2 != 0 && pCount != pSize)
    	b[i] = positive.get(pCount ++) ;				
    else if(nCount == nSize && pCount != pSize)
		b[i] = positive.get(pCount ++) ;
    else if(pCount == pSize && nCount != nSize)
		b[i] = negative.get(nCount ++) ;
}				

for(int x : b)
 System.out.print(x+" "); 
}
}